22 



INHERITANCE IN RABBITS 



Two of the offspring produced by cross 4 were mated with each other, 

 viz, 9 504 and $ 506. They produced a litter of 3 young, the character 

 of which is shown in table 7. 



TABLE 7. 



The deviations from the mid-parental ear-length are + 2, 12, and 

 4 mm. respectively, which lie within the limits of variation observed 

 among lop-eared rabbits purely bred. 



The range of variation is chiefly upward (plus), doubtless because of 

 the small number in the litter, which would make the food supply of the 

 individual better than usual. 



CROSS 5. HALF-BLOOD LOP FEMALE X LOP MALE 179. 



Female 167 was produced by a cross similar to cross 2, in which the 

 mother was a short-eared Himalayan rabbit (923), and the father the 

 male lop used in cross 3. She was mated with lop o" 179 and produced 

 3 litters of young, as indicated in table 8. 



The range of variation in ear-length in these 3 litters of rabbits is wide, 

 extending from 165 mm. in a rabbit 7 months old (having full-grown 

 ears) to 194 mm. in one only 18 weeks old, or to 200 mm. in one 30 weeks 

 old, a total range of 35 mm. The largest minus deviation from the mid- 

 parental ear-length is 5 mm. ; the largest plus deviation, 30 mm. ; the least 

 deviation from the short-eared parent is 35 mm., but from the long-eared 

 parent only 10 mm. Hence in this cross the long-eared parent is approx- 

 imated more closely than the short-eared one. This, however, is not of 

 necessity evidence of Mendelian recessiveness of the character long-ear 

 in 9 167. Another and, we believe, better way of viewing the matter is 

 this: 9 167 transmitted a greater ear-length than she had herself attained. 

 It is known that conditions which influence general growth, during the first 

 20 weeks, influence also ear-length. But at 20 weeks of age ear-growth 

 is practically complete, although growth in other respects continues some 

 time longer. It is possible, therefore, for an animal to be stunted in ear- 



